STRATIGRAPHICAL PART 



STRATIGRAPHY OF THE PERMO-CARBONIFEROUS IN 

 THE GLASS MOUNTAINS 



THE DIFFERENT BEDS AND THEIR FAUNAS 



One may divide all the Permo-Carboniferous of the Glass Moun- 

 tains into four horizons. The highest part is then the Tessey forma- 

 tion ; below it follows the Gilliam formation, which overlies the Vidrio 

 formation, below which exists some more richly fossil-bearing sedi- 

 ments. This subdivision is mainly based on the lithological character 

 of the beds, the Tessey formation being a rather unstratified or thick- 

 bedded dolomite, the Gilliam a medium and thin-bedded limestone and 

 dolomite, the Vidrio a thick-bedded gray, dolomite, the lowest forma- 

 tion a sequence of sandstones, shales and limestones, which are quite 

 generally fossiliferous. This portion includes a sequence of dolo- 

 mite, shales and sandstones in its upper part, then follows a 

 larger member of sandstone and below this a heavy mass of 

 limestone, which overlies a considerable quantity of thinly lami- 

 nated sandstone with beds of thick-bedded limestone. Below this 

 series which we call the Word formation, there is a mass of shales 

 alternating with rather thin or medium-bedded gray limestones and 

 thinly bedded cherts which we call the Leonard foniiafion. This 

 series is underlain by a mass of rather medium to thin-bedded, whitish 

 gray, rarely conglomeratic limestone, which we ha.ve called the 

 Hess formation. At the bottom of this series was discovered an 

 erosional unconformity, which although being of quite a considerable 

 importance to the east of the Glass Mountains (near Gap Tank) be- 

 comes more and more pronounced farther to the west, and has been 

 followed by Baker also south of the Southern Pacific Railway in the 

 Mt. Ord Range. We recognized the great importance of this un- 

 conformity and found that the greater part of the underlying 

 formation belonged to the Pennsylvanian ; these beds, mostly 

 shales, limestones and sandstones, are called the Gaftank formation. 

 The natural idea would have been to suppose that this unconformity 



